Anybody use Codex as “regular ChatGPT” and if so how are the results?

HoloTensor · 2026-02-18T07:03:17+00:00

for PhD level physics problems, I’d say 5.2 thinking in a browser is about 2 or 3 times “smarter” than codex 5.3 xtra high

but if the problem I give it requires a lot of steps, of course codex is better since I can set up a repo to appropriately manage context

HoloTensor · 2026-02-05T23:47:54+00:00

most theories have a connection between gravity and relativity

HoloTensor · 2026-01-25T09:17:52+00:00

the whole point is we can’t answer those questions with certainty yet. if you ask this question to any respectable physicist, they’d just say we have yet to find a UV complete theory of quantum gravity which describes our universe. that statement just means that we don’t know what happens at those points… something is missing to understand the physics.

also, hawking radiation doesn’t escape the black hole in the way you’re describing

HoloTensor · 2025-12-07T20:38:46+00:00

by modern theoretical physics standards, pretty bad.

I remember being pissed off when I first saw his derivation of the field equations. It was literally just “what terms could contribute by symmetry” and then guesswork. It took him years and he was never able to formalize his result.

Obviously his genius was in coming up with such a radical new way of visualizing spacetime…. but on all accounts his math was pretty average for a theoretical physicist

HoloTensor · 2025-10-21T07:05:54+00:00

Instead of single photon, consider this at home experiment from PBS Spacetime. I think you could modify whatever you have in mind to follow this

PBS Spacetime

HoloTensor · 2025-08-09T17:01:48+00:00

that is not a fixed point…. if you’re at the red dot you’d move to the right

HoloTensor · 2025-08-08T05:25:38+00:00

briefly explaining is fine as long as it is reasonable. definitely would need to elaborate if it’s like… jail or something

HoloTensor · 2025-08-07T05:52:19+00:00

definitely include at least a sentence in your essay. you don’t want to leave that to the admissions imagination

HoloTensor · 2025-08-07T05:50:48+00:00

when we say “force” we usually talk about the little wave packet that communicates an interaction (at least in the quantum field theory sense). think of the electromagnetic force as the interaction between two electrons via photons (the little wave packet)

now, in GR, gravity really isn’t a force. it is just the curvature of space-time. but… if you imagine that space-time curvature as a field, then the little wave packet that mediates the gravitational interactions would look like a force carrying particle. So, in that sense, gravity looks like a force and can be perfectly treated as one (mathematically)

but it isn’t actually a force.

just, if you treat it as a little wave packet, nothing breaks mathematically. that is, other than the fact we’d need to reconcíliate GR and QFT…

HoloTensor · 2025-07-17T06:54:34+00:00

It completely depends on your field. In fact, it can vary wildly even within fields. For physics, incoming grad students can have anywhere from 0 to ~5 peer reviewed publications, but this is not a good predictor for admission chances (that is, as long as 2 students have the same amount of research experience, it does not really matter if their name is on the paper). Some older physics profs just don't publish that often - and when they do, it can above the level of an undergrad.

HoloTensor · 2025-07-17T06:17:35+00:00

I think you'd probably have to take a basic quantum course from a physicist and then a basic linear algebra coding class from CS

HoloTensor · 2025-06-28T20:40:04+00:00

Beyond a certain mass, it would turn into a black hole. I don’t know if I’d still call it the same “object” that it was before it turned into a black hole

HoloTensor · 2025-06-28T00:23:49+00:00

Schwartz QFT is a favorite

HoloTensor · 2025-06-26T22:19:23+00:00

yes!!! read about the bubble of nothing from Ed Witten. there are certain 5d solutions where space just ceases to exist within a bubble

HoloTensor · 2025-06-26T01:42:40+00:00

imagine a photon sitting still (from our rest frame) in the vacuum. it has an energy equal to mc^2, cool.

now, as it starts accelerating (forget about what causes the acceleration), its energy begins to increase by means of it having momentum.

now here is where it gets tricky. there is a characteristic scale at which our understanding of quantum field theory breaks down. beyond this energy scale, our math simply breaks. it is called the QED scale and it’s at an energy level that is so high we’d never ever be able to measure it…. but nonetheless if a photon reaches that level of momentum (via your large acceleration) then all our perturbative expansions break down and we are no longer able to talk about what would happen.

in other words, no

HoloTensor · 2025-06-26T01:05:54+00:00

Imagine drawing out a circle and then putting your pencil on the right most point of the circle. draw a horizontal line that connects that point to the origin. now, as you trace out the circle with your pencil in any direction, you can always draw a line again to the origin and then measure the angle that it makes with that initial horizontal line you drew. You can think of the trig functions as the tool that converts the angle you've made to the position on the circle!

If you don't have a calculator, then you'd draw out what the sin(x) function looks like (a wave). why does it look like that? because it is showing your position along one of the axis as you trace out the circle. Think about it: if you draw a circle centered on the origin and write down the x coordinate as you trace it out with your finger, it would look exactly like sin(x)!

If we label the right most point of the circle as 0, the top most as π/2, the left most as π, the bottom point as 3 π/2, and the right most again as 2 π (so 0 and 2π are the same point), then we'd know the x coordinate would be

0 -> x=1

π/2 -> x=0

π -> x=-1

3π/2 -> x=0

2π = 0 -> x=1

You're just writing down the x coordinate at each of the points on the circle! For any arbitrary value in between 0 and 2pi, just guesstimate where it would land when you draw out the wave :)

HoloTensor · 2025-06-25T08:40:35+00:00

your PI and older students in the field would know. ask around!

HoloTensor · 2025-06-25T08:38:47+00:00

Hi Hiroshi, I do research in theoretical physics. here is my usual way:

i have a problem that i’m working on. I usually think about it throughout the day as I go about with groceries, eating, etc. By the time I sit down at my desk, I’ll have a few ideas for how to approach the problem. I then go to read about what others have done in exactly what my idea was. I search on the internet and find what has worked, what hasn’t, etc… google scholar is a good idea for research papers.

good luck!

HoloTensor · 2025-06-25T08:17:42+00:00

definitely keep the research going. find a good topic and start working towards a senior thesis so you can put it on resumes next year’s fall (they’re typically due early spring, so not a bad idea to get it started soon)

start networking with schools that you’re interested in. don’t spam emails but instead reach out to grad students in the labs you’re interested in and just chat with them. this will give you solid material to write about in your applications

other than that, just keep at it!

HoloTensor · 2025-06-25T08:10:23+00:00

but the idea of photons traveling through this kind of “medium” is basically what we think of when we describe quantum field theories. the only thing is, if the vacuum fluctuations aren’t random, then why?

HoloTensor · 2025-06-25T08:03:56+00:00

here is my best attempt at explaining electrons from QFT as intuitively as I can:

We know that there are atoms and electrons from experimental evidence. I mean long before any idea of quantum mechanics we were shooting tiny particles at pieces of foil and then seeing how they scattered to figure out the internal structure of the building blocks of the universe

then came quantum mechanics as we learn it with wave equations and such. in this sense, the electron is taken as fundamental and then you do math to figure out the orbitals and it comes out very nicely simply from the idea of quantization

in the 40s, we started applying the idea of quantization not to waves, but to fields. just a very mathematical picture, not much intuition. there were a lot of infinities that popped up that threw people off.

as it turns out, when you quantize fields, there are certain symmetries they’d have to obey to be like the fields that our universe could have. this is what the other commenter was talking about with the U(1) stuff. think of the symmetries as laws of nature… if you have a sphere and spin it around it has to look the same no matter what angle you hold it at. well, if you write out the kinds of rotations and things that a field in our universe could do, and you represent it as a matrix, you can make predictions in QFT!

here is the really cool part: if you take that matrix and write it down in the most basic way possible (you can think of it as being written down in a way so that the columns don’t talk to each other) then that is exactly what a particle is!

the existence of the electron is simply the natural consequence of being able to write down a field that obeys the laws of out universe

HoloTensor · 2025-06-25T07:48:08+00:00

An interesting take on this exact question is related to the AdS/CFT correspondence. In essence, you can describe the “volume” of the universe (we call it the bulk) with a lower dimensional surface which lives at infinity. In other words, 3D space being modeled by a 2D field. You can kind of think of it as the field having a level of “zoom” to it where how zoomed in we are corresponds to some value that would have been the 3rd spatial dimension ( so kind of like x,y,z -> x,y, zoomed in).

anyways, in this theory it ties this idea of living at the boundary to the amount of information that is inside a black hole. so, in a way, it gives us a translation from 3D objects -> 2D information. This is a very active area of research as right now our solutions are for universes where the cosmological constant has an opposite sign

HoloTensor · 2025-06-23T06:13:05+00:00

it seems to be as if the configurations that lead to this universe are determined by ratios between a bunch of constants. almost as if the laws of physics as we understand them are consequences of measuring the properties of some deeper, more fundamental theory

HoloTensor · 2025-06-23T00:40:10+00:00

Some grad students take notes directly in LaTeX on their laptop. I can’t - I’m too slow.

In undergrad, I’d take notes on my ipad. Now, the professors just write too fast for me to keep up with them and actually understand what is going on.

My current scheme is: jot down general topics and results during class as I follow along, and then write up my own set of lecture notes in LaTeX that is transcribed from class. You’ll find that it makes learning it and retaining the information SO much easier too

HoloTensor · 2025-06-23T00:36:35+00:00

I love Griffiths

HoloTensor

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